<?php

namespace App\Polls;

use App\Models\Poll;
use App\Models\PollResponse;
use Illuminate\Support\Collection;

/**
 * The results of a poll as CSV rows: one row per vote, one column per question.
 * Anonymous polls leave out who voted and when, and shuffle the rows.
 */
class ResultsCsv
{
    public function __construct(private Poll $poll, private string $locale)
    {
    }

    /** @return array<int, string> */
    public function header(): array
    {
        $identity = $this->poll->anonymous ? [] : [
            __('Voted'), __('Changed'), __('Profile type'), __('Profile'), __('Submitted by'),
        ];

        return array_merge($identity, $this->questions()->map(fn ($question) => $question->labelFor($this->locale))->all());
    }

    /**
     * Rows in chunks, so large polls are not loaded into memory at once.
     *
     * @return \Generator<int, array<int, string>>
     */
    public function rows(): \Generator
    {
        $questions = $this->questions();
        $query = $this->poll->responses()->with(['answers', 'voter', 'user']);

        if ($this->poll->anonymous) {
            // Shuffled, so the order does not reveal who voted when
            foreach ($query->inRandomOrder()->get() as $response) {
                yield $this->row($response, $questions);
            }
            return;
        }

        foreach ($query->orderBy('submitted_at')->orderBy('id')->lazy(200) as $response) {
            yield $this->row($response, $questions);
        }
    }

    private function row(PollResponse $response, Collection $questions): array
    {
        $answers = $response->answers->keyBy('poll_question_id');
        $cells = [];

        if (!$this->poll->anonymous) {
            $changed = $response->updated_at && $response->updated_at->gt($response->submitted_at->copy()->addSecond());
            $cells = [
                $response->submitted_at->format('Y-m-d H:i'),
                $changed ? $response->updated_at->format('Y-m-d H:i') : '',
                __(class_basename($response->voter_type)),
                $response->voter?->name ?? __('Deleted profile'),
                $response->user?->name ?? '',
            ];
        }

        foreach ($questions as $question) {
            $answer = $answers->get($question->id);
            $cells[] = $answer
                ? $question->questionType()->answerToText($answer->value, $answer->text, $question->settings ?? [], $this->locale)
                : '';
        }

        return array_map([self::class, 'safeCell'], $cells);
    }

    private function questions(): Collection
    {
        return $this->poll->questions()->get()->filter(
            fn ($question) => app(QuestionTypeRegistry::class)->has($question->type)
        )->values();
    }

    /**
     * Prevent spreadsheet formula injection: a cell starting with = + - @ (or a tab / carriage return)
     * would be run as a formula when the file is opened in Excel or LibreOffice.
     */
    public static function safeCell(string $cell): string
    {
        return $cell !== '' && str_contains("=+-@\t\r", $cell[0]) ? "'" . $cell : $cell;
    }
}